The present invention generally relates to telecommunication systems, and more particularly to a telecommunication system that can change the alerting pattern at a called terminal.
In the telecommunication systems that establish a line connection between terminals via a network, the incoming of a call is notified to the user at the called terminal by activating an alerting tone. In such a telecommunication system, there is a demand for the capability of changing the alerting tone depending on the terminal or the user from which the call has been issued such that the user at the called terminal can identify the calling terminal based upon the alerting pattern thus activated.
In order to meet such a demand, there exist terminals that can change the alerting tone based upon a predetermined keystrokes by the user at the calling station after the call is set up. The terminal having such a function generally assumes the automatic answering function that answers the incoming call automatically. There, one can set the terminal such that no alerting sound will be activated at the incoming of a call except for the case where the predetermined command is given from the calling terminal. If the command is not provided, the called terminal answers automatically to the incoming call and records the message sent thereto while not alerting the user of the incoming call. Only when the predetermined command is given, the terminal activates an alerting tone that may be different from the usual alerting tone and notifies the user of the incoming call. Thus, the terminal having such a function is useful for the user to reject unwanted calls. On the other hand, the user cannot generally distinguish the calling party based upon the alerting tone, as such a terminal provides only one special alerting tone other than the usual alerting tone. Further, such a telephone set is inconvenient in that the user at the called terminal is not alerted of the incoming call unless the predetermined command is given. One has to call back for the calls that are not brought to one's attention.
Further, there is proposed a telephone set in the Japanese Laid-Open Patent Publication 63-74354 wherein an audio guidance is issued to the user at a calling terminal after a line connection is set up. According to the reference, the audio guidance provided from the called station urges the user at the calling station to issue an identification code of the user and the telephone set that received the call activates an alerting tone corresponding to the user identification code when the same is provided.
Further, there is a variable alerting tone service provided by the vendor of the telecommunication network wherein a plurality of dial numbers are given to a single terminal in the network with respective alerting patterns. When a call occurs, the function of the called terminal is examined and the terminal is controlled by the network to produce the alerting tone in correspondence to the dial number that is used to set up the call to the called terminal, provided that the terminal is allowed to use the variable alerting tone service.
In the known system described in the Japanese Laid-Open Patent Publication 63-74354, however, it will be noted that the alerting tone is not activated even when the line connection is already set up, and there arises problems such as incurring of unnecessary fee. The same problem occurs also in the conventional system described previously. The service provided by the vendor of a telecommunication network also has a problem in that it uses a plurality of dial numbers for a single terminal and wastes the valuable resource of the network.